Traffic control system



Filed June 12, 1929 4 Sheets-Sheet l :ILII

/22 FIG //vvE NTbR FIG 3 v. DURBIN 2 ,051,369

- TRAFFIC CONTROL SYSTEM Aug. 18, 1936.

Filed June 12, 1929 4 Sheets-Sheet 2 By 714%, M

Aug. 18, 1936.

v. DURBIN TRAFFIC CONTROL SYSTEM Filed June 12, 1929 4 Sheets-Sheet 3 Fla '5 7 2 /N VENII'OI? 0 EYJ Aug. 18, 1936. v, D g 2,051,369

TRAFFIC CONTROL SYSTEM 750 744 I I /NVENTOR 7 FIG 8 71.41, M,

Patented Aug. 18, 1936 2,051,369 TRAFFIC CONTROL SYSTEM Vernon lDurbin, Newton, Mass, assignor to The Gameweil Company,

Newton Upper Falls,

Mass, a corporation of Massachusetts Application June 12,1929, Serial No. 370,306

17 Claims. (or. 177-337) The present invention relates to traffic control systems for intersecting ways.

A common type of trafiic control system embodies a uniform time sequence operation by which stop and go signals are flashed at definite time intervals without regard for the density of traffic oneither of the intersecting ways. This type of system is objectionable in that it causes unnecessary delay to vehicles approaching the stop signal while there is no trafiic on the cross-way.

Another type of automatic system employs a control which is normally set to permit flow of traffic on the more important way, while providing for an automatic shift of signals for a short period upon approach of a vehicle on the less important way. The automatic change of signals is usually effected acoustically or photo-electrically. Such systems are open to the disadvantage '2 that a stream of traflic on the less important way may hold up vehicles on the more important way for an indefinite period. If themechanismbecomes out of order, as is likely to happen, because I of the delicacy of the mechanism, traflic may be 25 delayed for long periods. Moreover, the signals are subject to change by tampering by irresponsible individuals.

One object of the present invention is to provide automatic means whereby a vehicle approaching the intersection on either way may act to gain control of the system to display the go" signal, but wherein the maximum time within which trafiic on one way may hold control of the system is limited.

Another object of the invention is to provide a system in which the signals normally change in timed sequence but in which the normal timing may be disturbed to permit a waiting vehicle to pass.

A further object of theinvention is to provide responsive means which is sufficiently sensitive to gain control of the system by passing or waiting trafiic, which is not likely to become out of order, and which cannot easily be rendered ineffective by tampering.

With these and other objects in view as will hereinafter appear, one feature of the invention comprises the combination of vehicle responsive means whereby a vehicle on approaching the intersection may act to bring about a change of signals if the go signal is not already displayed, together with sequential timing means whereby the signals are changed in any event at the end of a predetermined period. According to this feature, it is therefore impossible for trafi'c on one and particularly defined way, no matter how heavy it may be, to hold indefinite control of the system .to the exclusion of waiting vehicles on the other way.

Another feature of the invention comprises the combination of normally operating means to 5 change the signals in timed sequence, together with means operating upon the approach of a vehicle to the stop signal for effecting a n arly immediate advance of the change of signa s in the event that there is no traffic on the cross- 0 way. As an additional feature, the invention also provides for holding control of the system for a short period after. the passage of a vehicle through the intersection. Thus, a vehicle passing the go signal on one way holds control of the system for that way for a period of a few sec onds during which time a waiting vehicle stopped on the intersecting way may not gain control of the system. Thus, continuous trafilc on the way which shows the go signal may hold control of thesystem to the exclusion of vehicles on the other way but only for a maximum period determined by the normally timed sequential operation of the system. The means by which a vehicle gains control of the system to disturb the normahtlming of the signals is preferably automatic in that it responds to the presence of the vehicle without the necessity of any act on the part of the driver. The features of the invention as above described, however, are not limited to such automatic responsive means, but may be constructed to be operatedmanually, if desired.

As a further feature, the present invention contemplates a simple and effective form of responsive means which operates upon the approach or presence of a vehicle in its vicinity. This means comprises a normally balanced induction bridge, the characteristics of whosernagnetic circuit may be altered by the presence of a body of magnetic 1 material. Thereupon, the bridge becomes unbalanced and through the energization of the detector circuit, it is enabled to set the signal changing apparatus into operation. The responsive means of the present invention is advantageous in that while it is sufficiently sensitive to operate upon the approach of a considerable body of magnetic material, such as a nfirtor vehicle, it is not subject to unbalance by tampering.

Other features of the inventionconsist of certain novel features of construction, combinations and arrangementsof parts hereinafter described in the claims.

In the accompanying drawings illustrating the preferred form of the invention, Fig. 1 is a diagrammatic view showing the positions of the sigmil .device and the responsive means at an intersection of two ways; Fig. 2 is a plan view of one of the responsive devices; Fig. 3 is an elevation of one of the responsive devices set in the roadway; Fig. 4 is a plan view of the operating and controlling mechanism; Fig. 5 is a diagram of the electrical connections; Fig. 6 is a detail section on line 6-413 of Fig. 4; Fig. 7 is a'detail sectional view on line 7-4 of Fig. 4; and Fig. 8 is a development of. the advancement controlling cam.

General description-The invention is herein illustrated and described as embodied in a system for trafiic control at two intersecting ways shown in Fig. l as a north-south way--NS and an east-west way-EW. A signal tower ill of any usual or preferred form is located at the-center of the intersection. This tower contains two sets of lights, one of which is adapted to show on the north-south way and the other on the east-west way. Each set comprises three lights-a green light as a "go signal, a yellow light which is displayed near the end of the green signal to indicate that the red is about to come on, and a red light as a stop signal. The lights are normally operated sequentially by a predetermined time control in the usual fashion of automatic signals. The relative durations of the different signals may be adjusted in any desired manner, preferably with regard to the relative densities of traflic on the intersecting ways. The following specific sequence will be assumed in the description of the invention. The green light shows on NS for 40 seconds and the green and yellow together for 5 seconds. During this entire period of 45 seconds, the red light shows on EW. Then on NS the green and yellow lights are extinguished and the red light comes on for 45 seconds. For the first 40 seconds of this period, the green light shows on EW and for the remaining 5 seconds, the yellow light comes on with the green.

The sequential control is eifective to operatethe signals in the manner above described only when there is no traific in either direction or when no vehicles arriving at the intersection meet the red light or when there is a steady flow of traflic in both directions. In order to minimize the delay in the event of the approach of a vehicle to the red light while there is no trailic in the other direction, there is superposed on the sequential control an automatic control which is responsive to the approach of a vehicle and which initiates the operation of means to efiect a nearly immediate change of signals. Thus, a vehicle approaching the intersection gains control of the system through the automatic responsive means. If the red light is showing upon approach of the vehicle on NS, for example, while there is no cross trafiic on EW, the normal time sequence is thrown out, the EW tramc signal immediately displays the green and yellow lights for- 5 seconds, after which time the EW signal changes to red, and the NS signal to green. It is to be noted, however, that a vehicle approaching the red light gains immediate control'only in the event that no cross traflic is passing or has passed within a. predetermined period. Any vehicle approaching the intersection whether meeting the redor the green light, gains control for a predetermined time, say, about 3 seconds. Thus, if a vehicle approaches the red light on NS within 3 seconds after the passage of a vehicle on EW, the change of signals is delayed until the 3 trafiic on EW will not permit NS to gain control of the system and EW traihc will be permitted to pass unimpeded. The maximum length of time in which the EW trafiic may thus hold control of the system is, however, determined by the normal timed sequence of the lights. That is to say, no matter how heavy the traihc may be on EW, a waiting vehicle on NS is not obliged to wait more than 45 seconds.

Responsive devices.-The preferred form of responsive device or initiating means by which an approaching vehicle gains control or attempts to gain control of the system is shown in Figs. 2 and 3. This device comprises a sensitive induction balance arranged in the general form of a Wheatstone bridge which is normally in balanced condition but which is magnetically and electrically unbalanced by the presence of a body of magnetic material in proximity thereto. bridge comprises four inductance coils l2, I4, l6 and i8, mounted on the corners of a hollow rectangular base 29. Each coil is provided with an iron core 22. Four of these devices are mounted in the roadway near the intersection, as shown in Fig. 1, so that an approaching vehicle must necessarily pass over one of them. The devices are embedded in the roadway so that the upper surfaces of the magnetic cores are flush with the road surface. The base 20 is of such dimensions that the magnetic circuits of the inductances will be disturbed by the passing of a vehicle over or near them. Preferably the sides of the base 20 are somewhat greater than the width of an ordinary passenger vehicle. The inductances of each'device are energized by alternating current. The cores of diagonally opposite inductances l2 and iii are magnetized in the same direction while the cores of inductances I4 and iii are magnetized oppositely to those of inductances l2 and E8. The inductances are electrically connected as shown in Fig. 5, adjacent coils forming diago nally opposite arms of the bridge. Thus, for the south responsive device indicated at. s in Fig. 5, the arms l2 and I 4 are electrically connected as diagonal arms andthe coils l6 and i8 form the other diagonal arms. The bridge is connected to alternating current mains 24 and 25. The'detector circuit is connected in the manner usual to bridges and includes a relay 26 adapted to attract an armature 28 to close initiating switch contacts 30. Inasmuch as the relay operates most efiectively on direct current, a rectifier 32 is included in series wth the relay coil. Similarly, the east responsive device e is connected to operate a relay which controls an armature 36 adapted to close an initiating switch 38. The north and west responsive devices are not shown. The detector circuit of the north device leads to a relayfor lighting the lamps.

hicle comes over one of the responsive devices, the magnetic circuit characteristics are changed, thereby unbalancing the base 20 of each bridge is of slate or other nonmagnetic material, in order that.the variation introduced by the presence of a vehicle will be proportionately large.

switch 30 will be closed. These switches consti', tute a part of the initiating circuits by which a vehicle in proximity to one of the responsive devices acts to gain control or to endeavor to gain control of the system.

In the event that by unbalance of the bridge is too small toyactuate the relay, amplifiers of anyfusual form may be employed. I -Aslshown in Fig. 5, the-responsive devices are continuously energized fromthe alternating cur rent power mains. Obviously,- however, the sensitivity of the system is materially increased if the bridges are energized with current of relatively high frequency. However, sufilcient sensitivity is obtained with commercial alternating current without making the devices so sensitive asto be unbalanced by the accidental presence of, small bodies of magnetic material. Timed sequence operating system.-The signal tower has the two sets of lamps indicated-in Fig. 5, the red, yellow and green lamps-- R, Y and G for the NS way," and the corresponding lamps R, Y and G for'theEW'way. For the normal sequential control-of the system, these'lights are operated by four cams, namely, and'a yellow light control cam 46 for the NS system, and a similar set of cams 48 and 50 for the EW system. The cam 44 controls a switch 52 having a central movable contact" 54 and two stationary contacts 55 and 58. The cam 40 of the EW system controls a similarswitch 60. The cams 46 and 50'operatedouble contact switches 62 and 64 respectively. Considering the NS system, when the movable switch contact 54 is closed on the lower contact .58, the green light shows and when closed on the upper" contact 56, the red light is displayed. One contact of the switch 62 is connected to switch 52 and the other contact of the switch 62 is connected to the yellow'light. Electrical connections are suitably made to the lines 24 and 25 The cams of the EW system are identically arranged but displaced 180 from the corresponding NS cams. The cams are mounted, on a shaft 65 on one end of which is mounted a ratchet 68 (see Figs. 4 and 7). The ratchet is engaged by pawls I carried on a rotating'arm 12 andpressedinto engagement with the ratchet by springs 14. The carrier arm I2 is mounted on a shaft I6 tated by a motor I8 through reduction gearing 80.

In normal operation, the shaft 66 rotates continuously with the shaft I6, thereby driving the light control cams at a uniform rate.

In the specific eiiample assumed above, wherein V,

the red and green lights show alternately for p'eriods of equal length, the cams 44 and 4B are exactly similar but are displaced 180. Each of these cams is arranged to close the movable con tact on the upper contact of the switch for half a revolution .and to close it on the lower contact for the other half revolution. The cams 46 and 50 are also displaced 180? apart. Each has a dwell 18 of 20 to close 64 for seconds to display the yellow light.

Automatic responsive bridge. Preferably the Upon electrical unbalancing ofbne of the bridges, either the switch 30 or the 3 I '-'f the. operation of 'the switch the detector current; caused a master cam 44 the lower contact 58 of the which is continuously rotraction of an armature after its corresponding switch 02 on control.-The closing of mature 02. Similarly,the switch 30 controls energization-oi' an electro-mag'net 94 which is adapted .to'a'ttract an armature 96.- The magnet 90, how-- de-energized independently 30 at-a predetermined time prior to the change of signalsfrom green to red on NS, and similarly, the magnet 94 is arranged so that it cannot be energized for a short period preceding the change on EW. For convenience, the respective magnets are arranged evenis adapted to be to be positively de-energized at such times as the .green and yellow caution signals are displayed on their corresponding ways. To this end, the magnet 90 connects throng a wire 98 to a switch I00 which is operated by a cam I02 also mounted on the shaft '66,-"'I'he cam I02 maintains the switch I00 closed for 340 vided with a depression I04 of which opens the switch I00 at the same closes the switch 62. Similarly, the e'lectro-magnet 94 is controlled by a wire I06 in serieswith a switch I08 which is controlled by a cam H0 having a depressicn H2 to open the-switch at just the time that the switch 04 is closed by the cam 50.

- Thus, two initiating circu'ts are 'provided:-for

the NS way from the main 24 through detector switch 28, relay magnet90, wire 90, switch I00, and wire I I3 to the main and for the EW way, from the anain 24 through wire H4, switch 30, relay 94, wire I06, switch I08, and wire H3 to the main 25.

The armatures 02 and 96 are of the peculiar form shown in Fig. 0, and are so arranged as to be interlocking, that is to say, so that when one,

armature is attracted, it mechanically prevents attraction of the other armature. The armature 96 is pivoted to swing freelyon the drive shaft I6 and it is provided with an inwardly extending lower end H5 which tends to move the armature into retracted position by gravity. The armature 92 is similarly constructed and is freely pivoted upon a shaft H6 which is driven from'the shaft I6 but in the opposite direction by means of gears H0 and I20. Each of the armatures has a blocking foot "I22 which prevents attraction of the other armature when it is itself attracted. Pivoted on each armature is a pawl I24 which engages its corresponding gearwheel. The upper ends oi! the armatures are connected by a spring I26. It will be seen that if both armatures are in retracted position, attracted by its magnet unimpeded by the other armature. During an attracting movement, the pawl slides freely, over" the gear. However, rethe magnet is dea vehicle in proximity to one of the of its revolution and is pro time that the cam 46' one of them may be energized is retardedby the engagement of the pawl with the gear for a period of time depending upon the rate of the shaft. Thus, after one of the armatures has beenv attracted, the other armature cannot be moved into attracted position for a period of time determined by the retarded retraction of the first armature. This is preferably a period of about 3 seconds, for which time a. vehicle that has passed holds control of the system to the exclusion of a vehicle on the crossway. g Y

Double contact switches I20 and I30 are mounted adjacent to the respective armatures 02 and 96. These switches are normally open but are adapted to be closed by their armatures when the latter are attracted. To this end, each armature carries an insulating pin 1132 adapted to engage the upper switch contact.

Mounted on the shaft 66 is a-barrel cam [130, a development of which is shown in Fig. 8. The cam has a groove I36 to receive a pin 0:36 upon a cam follower lever Hi0 which is pivoted at M2. This groove is timed to move the lever in synchronism with the light control cams. The s1oping part I40 of the groove engages and moves the lever during the showing of the red light on NS. This groove is in length which corresponds to 40 seconds in the example given above. The straight part of the groove M6 during which no movement is imparted to the lever is 20 corresponding to a duration of 5 seconds. The inclined portion 646 is similar to the portion M6 but arranged to engage and move the lever during the showing of the red light on EW. The dwell I50 which holds the lever stationary is similar to the dwell I06. The upper end of the lever carries two armatures I52 and i541 which cooperate respectively with the cores I66 and 150 of electromagnets I60 and I62. During the normal sequential operation of the system, the magnets are de-energized and the armature swings idly over them. One or the other of the magnets is adapted to be energized by the closing of one of the switches 128 and I30. The switch H20 is connected in series with the electro-magnet it? which in turn is connected in series with a switch I64 controlled by a cam I66 on the shaft 66. The cam I66 is exactly similar to the light control cam 44 of the NS system and is so arranged that the switch I 64 is open when the green light is showing on NS, this being a time when a vehicle approaching on NS does not require a change of signal. Similarly, the switch 030 is connected in series with the electro-magnet H60 and a switch I 68 which is controlled by a cam t :70. The switch I68 is closed when the red light is showing on EW and is open when the green light is showing.

The switches IZB'and i313 are suitably connected to one side 24 of the mains and the switches E60 and I68 are suitably connected to the other side of the mains 25. Thus, two advancement controlling circuits arev provided, one for each way. For the NS way, the circuit comprises the advancement control switch 4 28, the magnet i 62 and the switch I64. For the EW way, the circuit comprises the advancement control switch 30, the magnet I60 and the switch I60. Considering the NS system, whenever the switches I26 and 864 are simultaneously then controlled by the cam groove 4) themagnet I62 is energized, thereby immediately attracting the lever I40 to its extreme position. Inasmuch as the cam groove is of steep pitch, the cam is advanced by the lever until the latter engages the dwell I46 of the cam groove. Therefore, the ratchet 68 overruns the pawl 70, immediately advancing the cams to such a position that the yellow light is displayed on the EW way. It will be understood that this action for NS can occur only when the switches E28 and I64 are" simultaneously closed, that is, only at a time when the red light shows on the NS way and the green light on the EW way. Similarly, the corresponding switches I30 and I 68 can be simultaneously closed only light on EW. The immediate advance of the shaft 66 and its associated cams lights the yellow closed (the lever I40 being when a vehicle approaches the red light in combination with the green on the EW way for 5 seconds, after which time the red light on the NS way changes to green. During the 5 second interval, the switch I08 is opened, thus opening the EW initiating circuit, so that no further change can be brought about by a vehicle approaching on EW. Therefore, if a vehicle approaching the red light on NS is able to gain control of the system by closing switch 5 28, its maximum wait will be 5 seconds. However, it may be that the approach of the vehicle will be ineffective to close the switch I28 because of the fact that the armature 92 may be blocked by the armature 96 in attracted position.

Opera ion-The operation of the system under difierent conditions of approach of vehicles on the two ways will now be explained.

When there is no trafiic in either direction, the

lights willopcrate in normal timed sequence.

- but is ineii'ective to energize the magnet i6? because the switch I 64 is open. fore, no change in the lights; of the passage of this vehicle is to hold control of the system for NS trafiic for the period that the armature 92 mechanically blocks the armature 96 (say, 3 seconds). :An EW vehicle now approaching, although it may cause the magnet 04 to be energized, cannot succeed in attracting the armature 96 the three seconds period has elapsed. If during that interval, another NS vehicle approaches, it again attracts the armature 02 and holds control for NS for another three seconds. The longest period, however, for which NS tramc may continuously hold the green light is determined by the normal timing of the system (forty seconds, with five seconds additional for the green and yellow caution signal). It will be noted that inasmuch as the. switch I00 is open when the green and yellow signal shows on NS, a vehicle on NS is unable either to gain or to hold control during the display of that signal.

-Attention may be here directed to the fact that it is. not essential for the switch I00 to operate in exact synohronism with the display of the caution signal. The purpose of the switch 900 isto open the NS initiating circuit at a sufliciently early time to permit the armature 92, if already attracted, to return to its fully retracted position prior to showing of the red signal on NS, thus unblocking the armature 96 and permitting a vehicle on EW to gain control of the system, The period during which either the switch I00 or the switch I08 is required to be opened is therefore the timenecessary for complete retraction of. the armature from fully attracted position, nofmatter what period may be determined upon for the showing of the caution signal. When the retraction period is less than the duration of the caution signal, the' periods may be and preferably are coincidentfas in the construction above described. It will be noted that the yellow light the signals changing directly from red to green, in which case also the provision for opening the initiating circuit near the end of the display of the green signal forms 'an important feature.

When a vehicle approaches the red light on There is, thg rethe only e ect to close the switch I30 until,

may be omitted altogether,

- secting ways.

NS, the armature 92 is attracted, if it is not blocked by the armature 96. vThereupon, the magnet I62 is energized, and the lever I 40 is immediately attracted to its lowest position, thus advancing the shaft 66 faster than the drive shaft 16, and bringing the cams to such a position that the yellow light is flashed with the green on EW. After five seconds, EW changes to red and NS changes to green to permit the waiting vehiclev to pass. Thereafter, the signals continue to flash in normal timed sequence until disturbed again in the manner above described. In the .event that trafiic on both ways is steady, neither will be able to gain control to throw the normal sequence out of operation.

It will be seen that the invention provides a control which operates practically in accordance with the relative densities of traiiic on the inter- Moreover, although permitting nearly unimpeded progress of steady traffic on one way, it does not disregard the rights of a single driver endeavoring to cross a busy thoroughfare. The longest time which a vehicle is required to wait is the normal time of display of the red light (forty-five seconds).-on the other hand, a vehicle approaching the red light may be permitted to pass in five seconds.

In the event that the automatic responsive means becomes out of order, the system as a whole is not rendered inoperative but works on its time sequence basis. It one of the bridges should become more or less permanently unbalanced, as by the breaking down of a car near it, it would not permanently hold control of the system to the exclusion of cross trafllc.

Although the system has been illustrated and described as employing an inductive bridge responsive means, which in itself forms a feature of the invention, it will be understood that the operating mechanism is not limited to control by any specific responsive means. Viewed in its broader aspects, the responsive devices form a means .for closing the initiating circuits at the switches I28 and I30, and for this purpose any suitable devices may be employed. For example, the initiating switches 28 and 36 might be closed manually by the driver of the vehicle.

Furthermore, such inductive bridge responsive means or detector mechanism is not herein specifically claimed, as same forms the subject matter of my c'o-pending application, Serial No. 88,640, filed July 2nd, 1936, as a division hereoi.

Although a specific description'has been given of one form of apparatus, employing signals of certain color operating normally in time se-.- quences of equal duration and for definite periods, it will be understood that signals of any desired form, color and arrangement may be employed and operated in any desired timing and sequence.

Having thus described the invention, what is claimed is:

1. A traihc controlsystem for intersecting ways having, in combination, a right of way signal device including a set of signals for each way, normally operative signal control mechanism to change the signals sequentially, driving means normally acting to drive the signal control mechanism at a uniform rate, and means involving traffic responsive mechanism for advancing the signal control mechanism with respect to the driving means to advance the change of signals out normal sequence without thereby affecting the order oi sequence. 2. A traillccontrol system for intersecting ways having, in combinationja right of way signal device including a set'of signals for each way, signal controlling mechanism normally operating tochange the signals in timed sequence, with predetermined timed intervals between changes driving means normally acting to drive the signal controlling mechanism at a uniform rate, an initiating circuit for each way, an advancement controlling circuit for each way, a switch in each advancement controlling circuit, means operated upon closure of the initiating circuit to close the corresponding advancement controlling switch and to obstruct closure of the other advancement controlling switch, and means operated by closure of an advancement controlling circuit to cause the signal controlling mechanism to overrun the driving means whereby to cause cancellation of substantially all of the unexpired portion of a then effective prechange interval.

3. .A trafiic control system for intersecting ways having, in combination a right of way signal device including a set of stop and go" signals for each way, signal operating mechanism, driving means for the signal operating mechanism acting normally to change the signals in timed sequence, with predetermined timed intervals between changes an initiating circuit for each way, a relay in each initiating circuit, having an armature, means for interlocking said armatures when one is attracted so that the other cannot be attracted, and advancement controlling mechanism operable upon a predetermined positioning of an armature to advance the signal operating mechanism with respect to the driving means whereby to cause cancellation of'substantially all of the unexpired portion of a then efiective prechange interval.

4. A traffic control system. for intersecting ways having, in combination, a right of way signal device including a set of stop and go signals for each way, signal operating mechanism, driving means for the signal operatingmeuhanism acting normally to change the signals in timed sequence, with predetermined timed intervals between changes, an initiating circuit for-each way,

a relay in each initiating circuit, having an arma-- tracted, means to retard retraction of an armature after being attracted, and advancement controlling mechanism operable upon a prededetermined positioning of an armature to advance the signal operating mechanism with respect to the driving means whereby to cause cancellation of substantially all of the unexpired portion of a then efiective prechange interval.

5. A traffic control system for intersecting ways having, in combination, a set of stop and go signals for each way, signal operating mechanism, driving means for the signal operating mechanism acting normally to change the signals in timed sequence, with predetermined timed intervals between changes, an initiating circuit for each way, a relay in each initiating circuit having a' pivoted and normally retracted armature, interlocking means preventing concurrent attraction of said armatures, a pawl on each armature, continuously rotating wheels engaged by said pawls for retarding retraction of a previously attracted armature, and advancement controlling mechanism operable upon a predetermined positioning of an armature to advance the signaloperating mechanism with respect to the driving means whereby to cause cancellation of substantially all of the unexpired portion of a then efiective prechange interval.

6. A trafflc control system for intersecting ways having, in combination, a set of stop and go signals for each way, signal operating mechanism, driving means for the signal operating mechanism acting normally to change the signals in timed sequence, with predetermined timed intervals between changes, an initiating circuit for each way, a relay, having an armature, in each initiating circuit, means for interlocking s'aid armatures when one is attracted so that the other cannot be attracted, an advancement controlling circuit for each way, means for closing an advancement controlling circuit when the armature of its corresponding'relay is attracted and the stop is displayed, and signal advancing mechanism to advance, the operating mechanism with respect to the driving means whereby to cause cancellation of substantially all of the unexpired portion of a then efiective prechange interval.

7. A trahic control system for intersecting ways having, in combination, a set of stop and go signals for each way, signal operating mechanism, driving means for the signal operating mechanism acting normally to change the signals in timed sequence, with predetermined timed intervals between changes, an initiating circuit for each way, a relay, having an armature, in each initiating circuit, means for interlocking said armatures when one is attracted so that the other cannot be attracted, an advancement con' trolling circuit for each way, a switch in each advancement controlling circuit, means operated by the signal operating mechanism for closing said switch when the stop signal is displayed on its corresponding 'way, an advancement controlling switch for each circuit operable upon' a predetermined positioning of its corresponding crating means with respect to the driving means when an advancement controlling circuit is closed whereby to cause cancellation of substantially all of the unexpired portion of a t en efiective prechan e interval.

8. A trafiic control system for intersecting ways having, in combination, a set offstop and go signals for each way, signal operating mechanism and driving means therefor normally acting to change the signals in timed sequence, with predetermined timed intervals between changes, an advancement controlling circuit for each way, means, for energizing an advancement controlling circuit upon approach of a vehicle to the stop signal on its corresponding way, and means operated by said circuit to advance the operating mechanism with respect to the driving means whereby to cause cancellation of substantially all of the unexpired portion of a then effective prechange interval.

9. A trafiic control system for intersecting ways having, in combination, a set of stop" and go signals for each way, operating mechanism normally acting to change the signals in orderly sequence, driving means for causing said mechanism to efiect such changes with pretimed intervals therebetween, vehicle responsive means for each way, an initiating device for each way responsively associated with the respective vehicle responsive means and having interlocking mechanism to prevent simultaneous operation of more than one initiating device, and means controlled by the initiating devices for advancing the operating mechanism with respect to the accreeo Y driving means whereby to cause cancellation of substantially all of the unexpired portion of a then eifective prechange interval.

10. A traffic control system for'intersecting ways, having, in combination, a set of stop and go signals for each way, signal operating mechanism and driving means therefor acting normally to change the signals in an uninterrupted' timed sequence, with predetermined timed intervals between changes, advancing mechanism including a device driven synchronously with the operating mechanism, and traffic responsive advance initiating means for causing actuation of said device to move the operating mechanism in advance of the driving means whereby to cause cancellation of substantially all of the unexpired portion of a then efiective prechange signal.

11. A tramc control system for intersecting ways having, in combination, a set of stop and go signals for each way, signal operating mechanism and driving means therefor acting normally to change the signals in timed sequence, with predetermined timed intervals between changes, advancing mechanism including 'a cam normally driven by the operating mechanism, a normally inactive cam follower, and means operated by approach of a vehicle to move the came follower to drive the cam, and thereby to advance the operating mechanism with respect to .the driving means whereby to cause cancellation of substantially all 'of the unexpired portion of a then efiective prechange interval.

12. A traffic control system for intersecting ways having, in combination, a set of stop and go signals for each way, signal operating mechanism and driving means therefor acting normally to change the signals in timed se quence, with predetermined timed intervals bearmature, and means to advance the signal op tween changes advancing mechanism including a device driven synchronously with the signal operating mechanism, advancement controlling circuits, one for each way, vehicle responsive means ,having provision for energizing one or the other of said advancement controlling circuits, a magnet in each advancement controlling circuit associated with to efiect acceleration of "the synchronously driven device to drive the signal operating mechanismahead of the normal timed control whereby to cause cancellation of substantially all of the unexpired portion of a then efiective prechange interval.

13. A traflic control system for intersecting ways having, in combination, a set of stop and go signals for each way, signal operating mechanism, driving means for the signal operating mechanism normally acting to change the signals in timed sequence, an initiating circuit for each way, vehicle responsive means for each way to energize the initiating circuit, cachinitiating circuit including an electro-magnet, re-

' layarmatures for the magnets, means for interlocking said armatures when one is attracted so that the other cannot be attracted,.mea.ns for retarding retraction of an armature after being attracted, means for opening an initiating circuit for a time suflicient to permit complete retraction of an armature prior to thechange from the go to the stop signal, an advancement controlling circuit for each way having a switch operable responsive to the signal operating mechanism except when the stop signal is displayed for rendering said advancement controlling circuit ineflective, means for energizing an advancement controlling circuit by energization of its corresponding initiating circuit, and means acting upon energization of and advancement controlling circuit to advance the signal operating mechanismahead of the driving means.

14. A trafllc control system for intersecting ways having in combination, a right of way signal device including a set of signals for each way for manifesting stop and go aspects therefor, means including signal control mechanism for normally changing the aspects of said signals in orderly sequence and driving means for causing said mechanism to efiect such changes with predetermined intervals therebetween, traflic responsive means associated with respective ways each operable during a go" aspect for some other way for advancing the signal control mechanism withrespect to the driving means to cause cancellation of substantially all of the unexpired portion of the interval determined pursuant to the pretiming to aspect and for establishment of a go aspect for the way of such operated means, and change delay means associated with the trafilc responsive means for each way and operable during a "go" aspect for its associated way for delaying any such cancellation.

15. A traffic control system for intersectingways having-in combination, a right of way signal device'including a set of signals for each way for manifesting stop and go aspects therefor, means including signal control mechanism for normally changing the aspects of said signalsin orderly sequence and driving means for causingsaid mechanism to effect such changes with predetermined intervals therebetween, traflic re-V sponsive means associated with respective ways each operable only following a predetermined portion of a go aspect for some other way for advancing the signal control mechanism with respect to the driving means to cause cancellation of substantially all of the unexpired portion of the interval allotted to such go aspect pursuant to the'pretiming, thereby to hasten establishment of a go aspect for the way of such operated means, and changedelay means associated with the precede termination of such go" trafllc responsive means for each way and operable during a go" aspect for its associated way for delaying any such cancellation.

16. A trafllc control system for intersecting ways having, in combination, a n'ght-of-way signal device includinga set of signals for each y, signals in orderly sequence, driving means for causing said mechanism to effect such changes with predetermined timed intervals therebetween, an initiating circuit for each" way, an advancement controlling circuit for each way, means acting upon closure of an initiating circuit tending to close the corresponding advancement control circuit and to prevent concurrent closure of the other advancement controlling circuit, and means operable upon closure of .an advancement controlling circuit Ior advancing the signal control mechanism with respect to the driving means to cause cancellation of substantially all of the unexpired portion of the then eiiective prechange interval.

1'7. A traflic control system for intersecting ways having, in combination, a right-of-way signal de vice including a set of signals for each way, signal control mechanism for normally changing the signals in orderly sequence, drivingmeans for causing said mechanism to effect such changes with predetermined intervals therebetween, an

initiating circuit for each way, means for automatically closing the initiating circuit upon approach of a vehicle, an advancement controlling circuit for each way, interlocking means operated by the initiating circuit to close the respective advancement controlling circuits and to prevent concurrent closure of both of said advancement interval associated therewith.

VERNON DURBIN.

signal control mechanism for changing the 

